Forwarded headers (e.g. X-AIMock-Context) were dropped before reaching the
wire in two cases. First, install_httpx_hook only attached to the immediate
client, missing an httpx client nested one or more ._client hops deep; it now
walks the ._client chain (bounded) to find the object that carries
event_hooks. Second, a sync def hook installed on an httpx.AsyncClient was
invoked as a coroutine and never awaited, silently dropping headers; the hook
is now async def for AsyncClient and sync def for Client. Async detection
prefers isinstance against the real httpx classes and falls back to an EXACT
"AsyncClient" MRO class-name match (not startswith("Async"), which would
misclassify a sync client whose MRO includes an Async*-named base).
Matches the CopilotKit runtime's extractForwardableHeaders() which
already forwards all x-* prefixed headers. Enables any custom
x-* header to propagate from browser through AG-UI to LLM calls.
ContextVar-based ambient state + httpx event hook. Incoming
x-aimock-* headers from AG-UI requests are forwarded to outgoing
LLM API calls. Keys normalized to lowercase. Warning emitted when
install_httpx_hook receives an unrecognized client type.
Jordan Ritter